DSpace@ATÜ (Adana Alparslan Türkeş Bilim ve Teknoloji Universiti)
Not a member yet
3463 research outputs found
Sort by
A comprehensive review of potential protection methods for VSC multi-terminal HVDC systems
No full textHigh voltage direct current (HVDC) transmission systems represent a significant development for future power systems due to presenting promising solutions for long-distance power transmission. However, the protection of HVDC systems is becoming one of the most significant challenges due to the extremely high short-circuit current within a short time span and the lack of zero crossing in the DC systems. DC protection schemes must detect and isolate the fault within 4-6 ms, while AC protection systems operate with considerably longer response times. Therefore, the techniques utilized for HVDC protection systems require more attention to enhance their performance in the future. This paper provides a comprehensive review of various protection techniques for HVDC systems, highlights recent advances, and analyzes the pros and cons of each method. Initially, different challenges of HVDC protection systems are presented, and then various HVDC protection schemes are discussed and classified into two groups based on the operation time. After that existing protection schemes are investigated in detail by including practical examples. The review aims to close the gap between the presented HVDC protection methods and technical challenges in order to overcome future issues of power system protection. Moreover, signal processing methods and artificial intelligence (AI) techniques, which play a key role in the future of protection systems, are extensively investigated to highlight the possible solutions. Finally, various recommendations, key challenges, and future trends with respect to the development of HVDC protection schemes have been presented for researchers and engineers studying in this field
ADAPTATION AND VALIDATION OF THE METEOROPATHY QUESTIONNAIRE TO THE TURKISH SAMPLE
No full textThe present study aimed to adapt and evaluate the psychometric properties of the Meteoropathy Scale (METEO-Q) for the Turkish population. Furthermore, it aims to suppress some limitations of the original study by examining construct validity and test-retest reliability, and associations between certain variables. A total of 603 participants (M=34,92, SD=13,57) were recruited. METEO-Q, Seasonal Pattern Assessment Questionnaire (SPAQ), and sociodemographic form were utilized to collect data. To test the construct validity, exploratory factor analysis and confirmatory factor analysis were carried out. The exploratory factor analysis result pointed out the presence of a two-factor structure. Two-factor structure exhibited a reasonable model fit in the confirmatory factor analysis. The two factors (meteorosensitivity and meteoropathy), structured checklist and, total score of METEO-Q indicated good reliability (alpha = .86, .88, .95, .93, respectively). Test-retest reliability scores demonstrated good reliability. TheMETEO-Q score was positively associated with SPAQ, gender, self-mutilation, and suicidal behaviors. In conclusion, the Turkish version of METEO-Q provides a valid and reliable measurement tool for the general population
Soil-geogrid interaction: The shear zone thickness of seafloor sediments with geogrid compared to filling materials
No full textIn geotechnical applications close to marine areas, using soil with rounded gravel that waves have left on the seafloor as fill material can help ensure the sustainable use of natural resources. However, typical fill materials have more shear strength than rounded sediments, but geogrids can solve the issue. Nevertheless, it is not well known how the grains' shape factors will affect the soil-geogrid interlocking mechanism and how the soil-geogrid interlocking based on grain shape will vary in the soil above and below the geogrid. This study aims to address the ambiguities specified. Therefore, three soil specimens were acquired, and the grains' shape parameters were determined using image processing. Subsequently, soil specimens were tested using large-scale direct shear (LSDS) and California Bearing Ratio (CBR) tests. Besides, LSDS tests were conducted by placing the geogrid at the shear surface, at different depths beneath the shear surface, and at varying levels above the shear surface to assess the soil-geogrid interaction distance. The findings showed that soil with seafloor gravels, using geogrid, could have the same shear strength as soil with crushed aggregates. Also, the highest shear strength was achieved when the geogrid was located below the shear surface by the maximum grain diameter
Effects of the Shaft Speed on Stiffness and Damping Coefficients of Hydrodynamic Bearing-Shaft System under Variable Viscosity
No full textThe rotating shaft-hydrodynamic bearings systems operated with high speed and/or heavy load conditions expose serious rotordynamics instability problems due to characteristics of the supporting bearings. The stability and the dynamics of these systems, directly relate to the lubricant properties that are directly affect by the heat generation. The main purpose of this study is investigation of the dynamic characteristics and the stability of a shaft supported by hydrodynamic journal bearing under variable viscosity. Th e equations of lubricant flow were derived by Dowson's model under variable viscosity, and the dynamic characteristics were modelled with the perturbation model in direct and cross directions. The heat transfers between oil and the journal surface was modelled in a 3-dimensional energy and the heat conduction equation. An algorithm based on finite difference and successive-over-relaxation method was developed to solve the theoretical models, simultaneously, and a serial simulation was performed to investigate the variations of the dynamic coefficients of the bearing-shaft system concerning the shaft speed for different radial clearance values. It was determined that the high speed increases the lubricant temperature, and so the static and dynamic performance characteristics decrease, moreover, this effect is more dominant for the smaller radial clearance
Polyvinyl alcohol: Starch based membrane scaffolds for tissue transparency requirements: Fabrication, characterization and cytotoxicity studies
No full textIn this study, the characterization and cytocompatibility of polyvinyl alcohol:starch (PVA:ST) based membrane tissue scaffolds developed for tissue transparency requirements in tissue engineering applications were evaluated in the presence of sodium dodecyl sulphate (SDS). In this context, two different amounts of SDS were added to the polymer structure of transparent membrane scaffolds to roughen the surfaces of PVA:ST membranes and to promote cell adhesion. In the light of this aim, three different types of membranes were created: A constant PVA:ST ratio of 9:1 (wt:wt) was used as a control and varying amounts of SDS (2 and 4 wt% of the total polymer amount) were added to the polymer solutions. Membrane tissue scaffolds were formed by freeze-drying method. Scaffold properties such as morphology, transparency, water absorption, chemical structure and cytocompatibility were investigated. In terms of physicochemical properties, it was observed that with the addition of SDS, the membranes had a rougher surface while retaining water retention and transparency. In cytotoxicity studies, the membranes were found to be non-cytotoxic and promoted cell proliferation as assessed by MTT assay. Furthermore, the PVA:ST membrane scaffold with 4% SDS added was able to promote the attachment, migration and proliferation of Mouse Embryonic Fibroblasts (MEFs) more than the control group. Overall, the results indicate that SDS-added PVA:ST scaffold membranes are suitable for human corneal stromal regeneration, wound dressing material and neural tissue engineering applications. © 2024 The Author
Experimental and analytical research on geopolymer concrete beams reinforced with GFRP bars
No full textThis paper presents the behavior of geopolymer concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars. In the study, ordinary Portland cement concrete and geopolymer concrete beams having GFRP bars were prepared and tested under four- point loading. The load- deflection diagrams and load capacities of the tested beams were obtained. It was observed that the tested beams exhibited good ductility and significant deflection capacity. The results showed that increasing the tension GFRP reinforcement ratio caused enhancement in the strength capacity of geopolymer concrete beams. In addition, the tested beams were analyzed to obtain the load capacity and the load- deflection responses. The theoretical load-deflection curves and load bearing capacities have been predicted well with the test results. Parametric study has been performed to determine the influences of concrete strength, shear span to depth ratio (a/d) and reinforcement ratio on the behavior of geopolymer concrete beams longitudinally reinforced with GFRP bars. It was concluded that increasing concrete strength led to an increase in load capacity. Besides, the ultimate load increased as the reinforcement ratio increased. On the other hand, increasing a/d ratio reduced the ultimate load value of GFRP reinforced geopolymer concrete beams.Adana Alparslan Turkes Science and Technology University Scientific Research Projects Directorate [21303012]The authors are grateful to Adana Alparslan Turkes Science and Technology University Scientific Research Projects Directorate (Project No. 21303012) for support The authors would like to thank to Ceylan Composite Company for providing GFRP bars
Development and Validation of the Isotretinoin Hesitancy Scale for Acne Vulgaris: A Preliminary Study
No full textBackground: Oral isotretinoin is the most effective systemic treatment for acne patients who fail to respond to other forms of therapies. However, hesitations and concerns regarding its side effect profile may detain the patients from treatment. This study aimed to develop and validate the Isotretinoin Hesitancy Scale (IHS) among acne patients. Methods: A cross- sectional study was conducted with 100 acne patients who had not used isotretinoin previously. A 22- item scale was created based on the related literature and expert opinions. The items of the scale related to beliefs and worries about isotretinoin were formatted with response options: agree, indecisive, and disagree. In this study, construct validity was tested with exploratory factor analysis, and reliability was tested with internal consistency and split- half reliability. Results: The results of exploratory factor analysis indicated a three- factor solution with a total of 14 items, explaining 57% of the total variance. The first factor (Hesitancy Related to Reversible Adverse Effects: 6 items) accounted for 30% of the variance, the second factor (Hesitancy Related to Irreversible Adverse Effects: 4 items) accounted for 16% of the variance and the third factor (Isotretinoin- related Anxiety: 4 items) accounted 11% of the variance. The internal consistency of the three factors was calculated as 0.79, 0.78, and 0.72, respectively. The Cronbach's alpha score of the total scale was found to be 0.81, and split- half reliability was found to be 0.87. Conclusions: The IHS is the first scale that provides a valid and reliable assessment of isotretinoin hesitancy in acne patients. Eliminating isotretinoin hesitancy may reduce acne- related clinical and psychosocial consequences
Effect of Ag-doping process into the yttrium iron garnet (Y3Fe5O12) thin films on the structural, magnetic and optical properties
No full textIn this work, the effect of Ag doping process (directly and as a nanoparticle) into the Y3Fe5O12 (YIG) thin films on the structural, morphological, optical and magnetic properties was studied in detail. Ag-doped YIG thin films were grown on thermally oxidized Si substrates by following sol-gel and spin-coating methods. All films were crystallized without cracks by two-stages heat treatment process. The XRD patterns confirm the formation of YIG peaks, and metallic Ag peaks which settled into the structure without bonding with the YIG components. In both Ag doping processes, the coercive field (H-c) and saturation magnetization (M-s) values of the samples containing 3% Ag are significantly lower than the other samples. The M-s values of 5% Ag doped samples were found the highest in both series. The M-s values of the films between in-plane and out-of-plane measurement increased with the Ag concentration. The optical measurements indicate an absorption peak in the range of 0-4 eV in both sample series and the optical band gap of the films decreased with the Ag doping due to its metallic characteristic. The ferromagnetic resonance measurements indicate that the lowest FMR linewidth as 92 Oe is seen in the 1% Ag-doped YIG sample. The relatively cheap and easy production of the used method and additive material may enable the widespread the usage of Ag-doped YIG thin films in magneto-optical devices.ukurova University Scientific Research CouncilNo Statement Availabl
Exploring the Current Practices and Future Directions in Project Management Education and Training
No full textIn light of the transformative influence of technologies and innovative methodologies associated with the Fourth Industrial Revolution, the paradigm of project management is undergoing a profound shift, prompting a re-examination of Project Management Education and Training (PMET). The escalating demand for project management expertise, juxtaposed with a scarcity of suitably qualified professionals, has yielded an increase in instances of faltering or challenging projects, thereby underscoring the amplified significance of PMET. A comprehensive assessment of the ongoing evolution of project management education and training is vital to shaping the trajectory of future educational strategies. In this context, bibliometric analysis has emerged as a pivotal tool, offering structured means to systematically present the expansive literature on PMET. This approach provides a panoramic view of the domain's development, facilitating a more informed understanding of its current contours which is paramount for crafting effective educational strategies. Employing bibliometric analysis as its methodological backbone, this study endeavors to discern the existing landscape of project management education and training. For this purpose, a comprehensive analysis was conducted on a dataset comprising 435 documents related to PMET, spanning the years 1985 to August 2023. The results of this analysis indicate that PMET publications are predominantly situated within the context of engineering education. A prominent theme that emerges from the literature is the discernible requirement for novel and forward-thinking strategies in PMET development, with a pronounced emphasis on the cultivation of soft skills and the integration of contemporary training methodologies, including gamification and simulation. In simple terms, the way we manage projects is changing a lot, and this has made us rethink how we educate and train people in project management. There's a growing need for experts in project management, but not enough qualified professionals to meet this demand. Because of this, we see more projects facing difficulties or failing, which makes the training and education of project managers even more important. To understand how project management education and training are evolving, we're using a special analysis tool called bibliometrics. This tool helps us organize and study a lot of information about project management education and training. By doing this, we can get a better idea of how this field is developing, which is crucial for making our education strategies more effective. In this study, we looked at 435 documents related to project management education and training from 1985 to August 2023 to get a clear picture of what's going on in this area
Property rights protection and intangible investment in the Sub-Saharan African non-financial firms
No full textThis empirical study examines the impact of property rights on intangible investments in subSaharan African (SSA) non-financial firms using firm-level data. The study employs a local projections methodology for twelve SSA countries over the period 1996-2020. Our empirical results show that property rights protection increases intangible investment in non-financial firms in the SSA region. This effect is significant for the SSA region in the long run.S&P Capital IQ for courtesyThis paper was prepared in the context of the Call for African Research Proposal. We would therefore like to thank Prof Rose Liao and Prof Jonathan Batten for their support during the review process. We would also like to thank the anonymous referee for valuable comments, which helped to make this version of the paper stronger. We also thank S&P Capital IQ for courtesy of providing data under this Call for its sponsorship. Of course remaining errors are our own